Śatapatha Brāhmaṇa ("of a hundred paths") 8.1.2.4

8.1.2.4

athottarataḥ | idamuttarātsvariti diśo vā uttarāttadyattā āhottarādityuttarā hyasmātsarvasmāddiśo 'tha yatsvarityāha svargo hi loko diśaḥ śrotraṃ ha diśo bhūtvottaratastasthau tadeva tadrūpamupadadhāti

And on the left (upper, north) side, with (Vâg. S. XIII, 57), 'This, on the upper side, heaven,'--in the upper sphere, doubtless, are the regions (quarters); and as to why he speaks of them as being 'on the upper (left) side,' the regions, indeed, are above everything here. And as to why he says, 'heaven (or, the light),' the regions, indeed, are the heavenly world (or world of light). The regions, having become the ear, remained above: it is that form he now bestows (on Agni).